AISC blodgett pdf free download
AISC blodgett pdf free download.Detailing to Achieve Practical Welded Fabrication.
The thousands of highway bridges, scores of high-rise buildings, and other impressive structures framed with welded steel certainly testify to the knowledge and skills of design engineers and structural steel fabricators. But, even sophisticated engineers do make mistakes— and there are very few designers or fabricators who are completely up-to-date on modern welding technology or structural design. The author, in his consulting work, often sees the errors that engineers make and has observed their lack of awareness of improved principles in design and advances in the welding arts. Before discussing examples of good and bad detailing, one point should be stressed: Anything done five years ago in welding design or fabrication could be obsolete! Every welded detail should be re-evaluated to determine (1) if it incorporates new knowledge about how to handle forces; (2) if it takes advantage of new provisions in governing codes; (3) if it is compatible with new advances in welding equipment, electrodes, processes, and procedures; and (4) if it offers opportunity to minimize costs through use of more precise determinations made possible with the advent of the programmable calculator.To show how changes have come about in structural design, refer to Fig. 1, reproduced from Design of Welded Structures, published by The James F. Lincoln Arc Welding Foundation. The first edition of this book appeared in late 1966. The photograph shows the welding of a connecting plate in a beam-to-column connection on a building in Miami. Obviously, this was considered a good technique in 1966—or it would not have been illustrated in the book. But that procedure is now obsolete, and the method of making the attachment is used sparingly. The welding was being done with a 5/32 ″ E6010 stick electrode. The electrode is good, but if one were to use this type of connection today and weld with a stick electrode, he would choose an electrode with a much faster deposition rate, probably an iron-powder type of a larger size. And with the welding done downhand, it would be much less costly to use the semiautomatic self-shielded flux-cored process, thereby achieving X-ray quality welds at still faster welding speeds. Obviously, in a revised edition, this photograph will not be used as an example of good practice. To get into the subject of detailing, it would be well to start with a dictum that is paramount in welded steel design: A path must be provided so transverse force can enter that part of the member (section) that lies parallel to the force. Figure 2 is illustrative of this principle. While it seems so elementary it is hardly worthy of mention, failure to provide such a path possibly leads to more structural design problems than any other cause. Figure 3a shows the simplest and most efficient way of welding a lug to a flanged beam so the force goes into the web, the part parallel to it.In Fig. 3b, the lug is placed across the bottom flange, which may require the use of either rectangular or triangular stiffeners to transfer the load to the web (see AISC Specification Sect. 1.15.5). Merely welding the lug across the more flexible flange would result in an uneven distribution of load to the weld and to the lug. Note the stiffeners are not welded to the top flange. There is no reason for such welds, since the flange will not take the force. In Fig. 3c, the member is in a different position, and the lug is correctly welded to the flanges, which will take the load. It is not welded to the web, since such welding would serve no purpose in transferring force. AISC blodgett pdf download.
